Heretofore beam lights, such as flashlights and the like, have generally used an incandescent bulb and a reflective surface to create a beam type lighting pattern or a collimated beam of light for general purpose use as a source of illumination. The bulbs give off light in a spherical pattern which ensures that a significant amount of light is reflected off the reflective surface surrounding the bulb, to create a beam of light. While these incandescent bulbs provide relatively uniform sources of a broad, visible spectrum of light, there are several problems that exist when using these bulbs in applications such as in a flashlight.
Incandescent bulbs are relatively inefficient which results in large amounts of entrapped heat energy, shortened life of the bulbs, and relatively high energy consumption of the batteries. The light produced from the incandescent bulbs is generally yellow and gives a yellowish tint to anything viewed by the flashlight. The incandescent bulbs are fragile and susceptible to breaking due to shock loads such as when the flashlight is accidentally dropped. The bulb life can also be limited by hot and cold temperature as well as vibrational effects. Additionally, because incandescent bulbs are inefficient in operation, there are increased operating costs.
Most recently, semiconductor LED lamps have been used in flashlight applications. An LED is essentially a PN junction semiconductor diode that emits light when a current is applied. The LED is a solid state device which operates at a low current and produces negligible heat. The LED is encapsulated in a resin material which protects the device making it durable and long lasting. The use of conventional semiconductor light emitting diodes solves the problems of entrapped heat, lamp longevity, frequent lamp replacement and higher current operation.
However, the light produced by current LED bulbs have a limited effective range, the small viewing angle created by the diode projects the light in a fashion such that when used in a flashlight or like device, the majority of the light does not hit the reflective surface of the flashlight's reflector. In addition, when an LED is simply inserted in place of an incandescent bulb, the LED lamp life is shortened because the current applied is in excess of what the lamp was designed to operate at. In general, simple replacement with a conventional LED into a typical flashlight will operate at 100-120 mA, while LED's are typically designed to operate below 30 mA. Another problem that exists when using conventional light emitting diodes is that of a non-uniform distribution of emitted light energy.
Shown in FIG. 1 is a sectional view of a conventional LED lamp having one or more semiconductor chips 150. The transparent envelope 100 has a convex hemispherical shaped lens 120, located at the end of a cylindrically shaped rod 140. A semiconductor chip 150 is mounted to the conductive surface of the first electrode, LED anode 110, within the convex reflector 140. A fine wire 130 connects the opposite end of the semiconductor chip 150 to the second electrode 120. Also shown is the cone shaped light pattern 160 that is emitted from this LED device. A beam of visible light projects in a cone that ranges in angularity from 12 to 36.degree. dependent upon the intended design usage.
The viewing angle 2 of the emitted light and visibility of the light produced by the diode 1 shown in FIG. 1 is relatively small making the device useful for indicators, and in some close range applications such as penlights or the like. In order to overcome this problem, some prior art devices use a cluster of LED's mounted together in an attempt to create stronger intensity light. These devices consume more energy, produce more heat, and are subject to produce dark spots due to averaging effects of the beams of light.
Therefore, there is a particular need for a light emitting diode lamp that provides a source of radiant energy that is adapted to distribute the radiated light energy onto a reflector to create a beam type lighting pattern and/or a collimated beam of light.